# LDOs, buck converters and PMICs

How a battery or adapter is turned into the steady voltages a chip needs, and why the choice of regulator matters for battery life.

Page: https://dharanova.com/learn/regulators · Track: Power · Level: Core · Facts last checked 6 October 2026

Read first: [Writing a power budget](https://dharanova.com/learn/power-budget.md)

Diagram: Four rows. LDO: 5 V in, 3.3 V out, the difference leaves as heat, and efficiency is at best about Vout/Vin, roughly 66%. Buck converter: a switch feeds an inductor that stores energy; it can exceed 90% at moderate loads, at the cost of switching noise, more parts and often poorer efficiency at very light loads. Quiescent current, not to scale: a regulator drawing tens of µA with no load against the rest of a board sleeping at a few µA. PMIC: one chip with three regulators whose rails come up in a fixed order over time, with a marker for reset control.

## Key points

1. A linear (LDO) regulator burns the difference between input and output voltage as heat, so its efficiency is at best about Vout/Vin: roughly 66% when dropping 5 V to 3.3 V. [1]
2. A switching buck converter stores energy in an inductor and can exceed 90% efficiency at moderate loads, at the cost of switching noise, more parts and often poorer efficiency at very light loads. [2][3]
3. Quiescent current is the regulator's own consumption with no load. It matters most in battery devices that sleep: a regulator drawing tens of microamps can use more than the rest of a board that sleeps at a few. [1][3]
4. A PMIC (power-management IC) combines several regulators with power sequencing and reset control in one chip, and is common on application-processor boards that need many rails brought up in a fixed order. [4]

## Where to go next

- [Designing for power that cuts out](https://dharanova.com/learn/unreliable-power.md): Power cuts and voltage dips are common in many places. A device should handle them safely and recover on its own.

## Sources

1. [Understanding the Terms and Definitions of LDO Voltage Regulators (SLVA079)](https://www.ti.com/lit/an/slva079/slva079.pdf), Texas Instruments
2. [Basic Calculation of a Buck Converter's Power Stage (SLVA477)](https://www.ti.com/lit/an/slva477c/slva477c.pdf), Texas Instruments
3. [TIDA-00393: Adding an LDO for Increased Standby Mode Efficiency (TIDUAA4)](https://www.ti.com/lit/ug/tiduaa4/tiduaa4.pdf), Texas Instruments
4. [i.MX 8M Mini Hardware Developer's Guide (IMX8MMHDG) Rev. 4.1](https://community.nxp.com/pwmxy87654/attachments/pwmxy87654/imx-processors/218788/1/IMX8MMHDG-NEW.pdf), NXP